(a) Field of the Invention
The present invention relates to a method for manufacturing a resin-sealed semiconductor device mounted on a circuit substrate of a hybrid IC and, more particularly, to a method for treating outer leads of the semiconductor device after sealing the semiconductor device with resin.
(b) Description of the Prior Art
The conventional resin-sealed semiconductor device mounted on a circuit substrate of a hybrid IC has been manufactured as follows.
A pellet which has been formed was first fastened onto a bed of a leadframe formed by punching a metal plate. A bonding pad of the pellet and the inner lead portion of the leadframe were then electrically connected by wire bonding.
Subsequently, the pellet and the inner lead portion of the leadframe in which the pellet are arranged are sealed by resin using molding dies. Thus, as shown in FIG. 1, the resin sealer 11 for containing the pellet is formed integrally with the leadframe 12. In the step of sealing with resin, the molding resin 13 flows out from the gap of the molding dies, adheres to the surface of the outer leads 12a and cures. FIG. 2 is a sectional view, taken along the line A--A' in FIG. 1. As shown in FIG. 2, since the outer leads 12a make contact on the upper and lower surfaces with the dies, the amount of the resin 13 leaked and adhered to the upper and lower sufaces of the outer leads 12a is extremely small. However, since the outer leads 12a make less contact on the sides with the dies, the resin 13 thickly adheres to the sides.
In order to, therefore, remove the resin 13 adhered to the outer leads 12a, a blasting with particles must be executed.
Then, the outer leads 12a are plated, for example, by soldering, and the unnecessary frame of the leadframe 12 is cut out to manufacture a product.
However, in the conventional blasting step, it was frequently difficult to completely remove the resin 13 adhered to the sides of the outer leads 12a.
Thus, when the outer leads 12a are plated in the next step, the outer leads 12a, from which the resin 13 on the sides is removed, are covered by a plating 14 on the entire periphery as shown in FIG. 3. However, the outer leads 12a, to which the resin is adhered on the sides, are plated only on the upper and lower surfaces as shown in FIG. 4. Therefore, the outer leads 12a shown in FIG. 3 are preferably bonded to a circuit substrate when mounted on the circuit substrate as shown in FIG. 5. However, the outer leads 12a shown in FIG. 4 are bonded to the circuit substrate in small adhering area as shown in FIG. 6, thereby causing the outer leads 12a to be improperly adhered to the circuit substrate. In FIGS. 5 and 6, reference numeral 15 designates a circuit substrate, and reference numeral 16 is a soldering material.
In case the leadframe 12 is formed by punching, even if the outer leads 12a having burrs 12a', 12a' as shown in FIG. 7 are covered by plating 14, a soldering material 16 is prevented from being fastened onto the outer leads 12a as shown in FIG. 8 when the outer leads 12a are mounted on the circuit substrate 15, thereby feasibly causing the outer leads 12a to be incompletely bonded to the circuit substrate 15.